UNITRACC - Underground Infrastructure Training and Competence Center

Terminology and definitions

Sep 11, 2008

Shafts

(Image: Planning)

In trenchless installation, shafts are the only structures that must be installed in the open-cut method of construction.

(Image: Attention!)

In the interest of minimising the environmental disturbance as well as the construction costs associated with this, great importance is attached to the following planning aspects:

Selection of the location
Quantity
Form and dimensions
Shaft construction method and support.

Sep 11, 2008

Shafts - selection of the location and the number

(Image: Attention!)

In the lay out of the line the concerns of the jacking method to be applied must be taken into consideration:

short or long distance jacking project
usage of a starting or target shaft for the jacking of several distances

(Image: Utilisation of a shaft for several jackings [Stein05a])

The locality and the number of shafts are greatly influenced by the lay out of the planned line to be jacked.

Sep 11, 2008

Jacking by means of an underground starting and target galleries

If starting and target shafts cannot be installed into the line axis directly, it is possible to create underground starting and target galleries, which are served from an access shaft sidewise of the line.

(Image: Jacking with the aid of underground start and target galleries with reference to [Ito98] [Image: S&P GmbH])

Sep 11, 2008

Shafts - shape and dimensions

The shape and dimensions of shafts should be planned and built under the aspect of minimising expected emissions and construction costs as well as work and health protection.	(Image: Cross sectional shapes of starting and target shafts)
(Image: Attention!) Shafts in which work is carried out must have sufficient working space. The dimensions of the working space depend on the slope angle, lining, equipment, type of pipe and method of working […

Sep 11, 2008

Length and width and/or diameter (starting shaft)

(Table: Dimensions of starting shafts - important parameters [FI-Steina])
(Image: Starting shaft dimensions for jacking pipes of 2.43 m lenght for rectangular shape of shaft and sheet pile wall lining for pre-defined microtunnelling or shield machine and jacking station [FI-Toyot])	(Image: Starting shaft dimensions for jacking pipes of 2.43 m lenght for rectangular shape of shaft with semi-circular rounded faces and lining of liner plates for pre-…

Sep 11, 2008

Length and width and/or diameter (target shaft)

(Table: Dimensions of target shafts - important parameters [FI-Steina])
(Image: Target shaft dimensions for square shape of shaft and sheet pile wall lining for pre-defined microtunnelling or shield machine and jacking station [FI-Toyot])	(Image: Target shaft dimensions for circular shape of shaft and lining with liner plates for pre-defined microtunnelling or shield machine and jacking station [FI-Toyot])

Sep 11, 2008

Work space widths in shafts when installing manholes

(Image: Working space widths for the erection of structures in building pits with reference to [TBG93a])

Sep 11, 2008

Shaft depths

(Image: Attention!)

The depth of the shaft depends on the pipe to be jacked, the soil removal concept of the jacking method and the structural conditions of the shaft excavation (buoyancy prevention, embedded length etc.).

(Table: Application possibilities …

Sep 11, 2008

Methods for securing shafts

(Image: Methods for securing shafts [Stein05a])

Sep 11, 2008

Fundamentals

Sep 12, 2008

Universal shaft construction

Definition universal shaft construction

Universal shaft construction:
Construction of unlined and lined shafts in accordance with DIN 4124, which are excavated manually or mechanically [Stein05a].

In principle, one distinguishes in universal shaft construction between:

Unlined shafts
Shafts with removable linings
Shafts with non-removable linings

[DIN4124:2012]

(Image: Securing of trenches and shafts without lining with reference to [DIN4124c] - Vertical sloped walls)

(Image: Standard …

Sep 12, 2008

Universal shaft construction

Selection of a suitable type of lining in universal shaft construction

(Image: Diagram for the selection of a suitable lining type in universal shaft construction)

Sep 11, 2008

Universal shaft construction

Sep 12, 2008

The simplest application form is presented by shafts with sloped walls.

The inclination of the slope is suited to:

the subsoil (physical properties of the in-situ soil types, water conditions),
the utilization of the adjoining surfaces (traffic paths, structures),
the expected loads by construction equipment,
the height of the slope and
its probable stability time.

(Image: Attention!)

If there is groundwater, then the water level must either …

Sep 12, 2008

Shaft securing without lining in accordance with DIN 4124

(Image: Securing of trenches and shafts without lining with reference to [DIN4124c] - Vertical sloped walls)

Vertically sloped walls

(Image: Securing of trenches and shafts without lining with reference to [DIN4124c] - Vertical sloped walls with sloped edges)

Vertically sloped walls with sloped edges

(Image: Securing of trenches and shafts without lining with reference to [DIN4124c] - Vertical sloped walls with sloped edges (variant))

Vertically …

Sep 12, 2008

Permissible slope angles without calculative verification of the stability

(Image: Permissible slope angles for trenches and shafts for non-cohesive or soft cohesive soils with reference to [DIN4124c] [Image: S&P GmbH])

Non-cohesive or soft cohesive soil

(Image: Permissible slope angles for trenches and shafts for at least firm cohesive soils with reference to [DIN4124c] [Image: S&P GmbH])

At least firm cohesive soil

(Image: Permissible slope angles for trenches and shafts for rock with reference to [DIN4124c] [Image: …

Sep 12, 2008

Verification of stability

(Image: Attention!) According to DIN 4124, the stability of unlined walls must be verified with the calculation method of DIN 4084 or by a subsoil report. The introduction of the jacking forces into the slope wall must also be specially proven to be safely arranged. [DIN4124:2012] [DIN4084:1997]
(Image: Unlined, sloped starting shafts - In microtunnelling with hydraulic spoil removal [FI-Herreb])	With increasing depth, the excavation volumes …

Sep 12, 2008

Prerequisites for the use of unlined shafts

Prerequisites for the use of unlined shafts:

observation of a minimum clearance between slope edge and vehicles/construction machinery (load-free protective strip at the slope edge)
no effect of dynamic loads
no flow of strata water into the shaft
no fissures or dislocation in rock

Sep 12, 2008

Advantages and disadvantages of unlined shafts

(Image: Pros and cons)

Advantages of unlined shafts:

simple creation
special devices are not necessary
lining material not necessary
noise-free and vibration-free method of construction
use of large machinery for excavation as well as the building of the structure is possible without impediments as no bracing structures are necessary
compaction of the backfilling against the in-situ soil

Disadvantages of unlined shafts:

great space requirements…

Sep 11, 2008

Unlined shafts

Sep 12, 2008

Horizontal lining - standard lining

(Image: Standard horizontal lining to DIN 4124 (means of fixing not shown) with reference to [DIN4124c] [Image: S&P GmbH])

With standard horizontal linings to [DIN4124:2012], the shaft walls are progressively lined during the excavation from the top to the bottom with horizontal, closely fitted wooden planks, sheet planks or similar and these are usually secured with vertical wale timbers and supported by bracing [Riege00b].

Prerequisite

The …

Sep 12, 2008

Removable (or reusable) linings in trenchless installation are understood to be coverings and bracings which, after completion of the jacking works, can be removed without danger by filling up the shaft again and which do not remain in the subsoil permanently.

Types of removable linings are:

horizontal lining
vertical lining
lining systems
supporting planks wall

(Image: Standard horizontal lining to DIN 4124 (means of fixing not shown) with reference …

Sep 12, 2008

Advantages and disadvantages of standard horizontal lining

(Image: Pros and cons)

Advantages of standard horizontal lining:

light lining elements
good adaptability especially with crossing pipelines
frequent re-use possible
compaction of the backfill against the in-situ soil

Disadvantages of standard horizontal lining:

soft lining, danger of subsidence for neighbouring structures or traffic surfaces
wage and time intensive due to manual activities
limited space for movement due to close bracers spacing…

Sep 12, 2008